What does the shield of faith really mean?

Something that has been dwelling on my mind quite a lot recently is the question: what is the armor of God; in particular what is the shield of faith?

 ¹⁰ Finally, be strong in the Lord and in the strength of his might. ¹¹ Put on the whole armor of God, that you may be able to stand against the schemes of the devil. ¹² For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. ¹³ Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand firm. ¹⁴ Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness, ¹⁵ and, as shoes for your feet, having put on the readiness given by the gospel of peace. ¹⁶ In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one; ¹⁷ and take the helmet of salvation, and the sword of the Spirit, which is the word of God
Ephesians 6:10-17

When we people of 21st century western culture think of the Christian armor, he thinks of the knight in shining armor, riding in on his white steed, or standing alone on a hill, wielding his mighty sword.

This just isn't the case.  When Paul wrote the verses describing the armor, in particular the shield, both he and his reader would have had a very different mental picture.  The reader in Paul's day would have pictured one of two things: the Greek phalanx,

or the Roman legion.

These units find their strength in their unity.  They are strong because they fight as one. 
I know this is the idea that Paul is trying to convey for the Christian for a few reasons. 
1. Because of what has been mentioned, the historical context of the Greek and Roman armies. 
2. Because Paul speaks on the armor of God right after speaking on unity in the church and working together as members of the body, as slaves and masters (employees and bosses in our context), husbands and wives, and children and parents.  He goes straight from that discussion to the discussion on spiritual warfare and the armor of God.
3. Because of a principle taught in Ecclesiastes 4

⁹ Two are better than one, because they have a good reward for their toil.   
¹⁰ For if they fall, one will lift up his fellow. But woe to him who is alone when he falls and has not another to lift him up!  
¹¹ Again, if two lie together, they keep warm, but how can one keep warm alone?  
¹² And though a man might prevail against one who is alone, two will withstand him—a threefold cord is not quickly broken.
  
So what is the point?  We must learn that when Paul is talking about the armor of God, he isn't talking about individuals fighting sin as is so often proclaimed from pulpits across America today.  The preachers say that, "You have been called to fight sin," or, "You need to take up the whole armor of God."  When in all reality, they should be crying out: "We must take up the armor of God.  We must fight sin together."  It is our unity that gives us strength.